The Expression Core will determine the developmental times and tissues in which candidate genes identified by Projects I, II and III are expressed. These studies will determine both RNA and/or protein expression patterns using immunohistochemistry or in situ hybridiation, whichever is deemed appropriate. Further, genes of particular interest will undergo analysis using the RCAS-TVA system for tissue expression of both wildtype and dominant negative proteins. Diaphragm whole mounts are difficult to examine, but the director and staff of this core have learned the necessary techniques from Dr. Akerman. Lung organ culture has been in use in the lab for 20 years. RNAi technology has been used by the Pis for the past 8 years. Together with the Drosophila Core, RNAi technology will be uniquely available for the program project. Brief descriptions of the protocols that Dr. Loscertales uses routinely which will be instrumental in analyzing CDH candidate genes follow.